Effect

Generations III and IV

As long as the user remains in battle, opponents cannot use any move which is also known by the user (including Pokémon switched in after the move was used). If the user's moveset changes while Imprison is in effect (such as by Mimic, Sketch or Transform), opponents are prevented from using the new moves.

Imprison will fail if no opponent possesses a move the user knows at the time Imprison is used.

If the target of this move runs out of PP of the rest of its usable moves, it will Struggle.

Generation V onward

Imprison will still execute even if no opponent has a move the user knows; though it has no immediate effect in such a case, if the opponent is able to change its moveset (e.g. Mimic, Sketch, or Transform) or switches out for a different Pokémon, it will be prevented from using the user's moves.

In Triple Battles, non-adjacent opponents are prevented from using moves that the user knows.